Project Grover: add wifi rate vs. range test case in Autotest.

 - fix export/unexport file path (attenuator_*.py)
 - update testbed config w/ new IPs in lab cell
 - remove 2.4GHz test case (can't be run until h/w upgrade)
 - add new 5GHz test cases for UDP and TCP
 - add new iperf option (bufsize) and set test timeout
 - add test method 'rvr_test' to use in Grover test bed

BUG=chrome-os-partner:16414
TEST=Manual (run network_WiFiRateRange/002* and 004* in grover lab cell)

Change-Id: I8017e4acfdd30e8a390388de7dd78ec8ba2459e2
Reviewed-on: https://gerrit.chromium.org/gerrit/39210
Reviewed-by: Paul Stewart <pstew@chromium.org>
Tested-by: Tan Gao <tgao@chromium.org>
Commit-Ready: Tan Gao <tgao@chromium.org>
8 files changed